1. Field of the Invention
This invention relates to a damper, and more particularly, to a torsional damper for absorbing torsional vibration occurring in a rotation driving system such as a crankshaft of an internal combustion engine, or the like.
2. Description of the Related Art
Conventionally, a torsional damper connecting a hub with a massive body via an elastic body of a rubber-like elastic material has been well known, and as a kind of it, a fitting type torsional damper has been known which is formed by press-fitting an elastic body of a rubber-like elastic material into a space between the hub and the massive body from either direction of the shaft.
However, since this fitting type torsional damper is not bonded by vulcanization adhesion, there is such an inconvenience that slides occurs, at a time of a heavy load condition, between the hub comprised of metallic parts and the elastic body or between the massive body comprised of metallic parts and the elastic body in the direction of the rotation.
To increase (improve) a slide torque for preventing this slide, mechanical methods have conventionally been employed such as a fitting surface of the hub or the massive body is treated by shot-blasting or the like to give these surfaces unevenness, or stickiness is provided on a surface of the elastic body, etc. However, either of these methods has had an insufficient effect so far.
For example, as is described in Japanese Patent Tokkai Sho 60-141532, adhesives such as a chlorinated rubber as a main ingredient is applied to a place between the hub and the elastic body or a place between the massive body and the elastic body. However, a conventional adhesive has an insufficient effect in an adhesive strength, or to the contrary, an adhesive strength is so tight that ill influence on other properties such as durability or the like tend to come out.
In view of the above-mentioned aspects, an object of the present invention is to provide a fitting type damper permitting to substantially increase a slide torque, especially, to provide a fitting type damper permitting to substantially increase a slide torque at initial stage as well as a slide torque even after heat-aging, endurance tests, or the like.
Another object of the present invention is to provide a process for manufacturing a fitting type damper permitting a substantial increase in slide torque at an initial stage as well as a slide torque even after heat-aging, endurance tests, or the like.
In order to achieve the above objects, the damper according to this invention, in a fitting type damper formed by press-fitting an elastic body of a rubber-like elastic material between the hub and the massive body in either direction of the shaft, has polymethylene-polyphenyl-polyisocyanate as a non-slide agent which is interposed between said hub comprised of metallic materials and a boundary of said elastic member or between said massive member comprised of metallic materials and a boundary of said elastic member.
It is an object of the present invention to increase a slide torque by a chemical method instead of a conventional mechanical method mentioned above and to increase a holding power of a metallic part and an elastic body by interposing a non-slide agent between the metallic parts and the elastic body (rubber). As a result of our intensive research to obtain an excellent sliding torque and also to avoid a deteriorating influence on other properties, polymethylene-polyphenyl-polyisocyanate has specifically been determined as a kind of the non-slide agent.
Polymethylene-polyphenyl-polyisocyanateis is shown by the following formula: 
Wherein nxe2x89xa70.
Polymethylene-polyphenyl-polyisocyanate is interposed between the hub comprised of metallic parts and the boundary of the elastic body, or between the massive body comprised of metallic parts and the boundary of the elastic body and non-slide effect can be obtained respectively. Another applying method is that polymethylene-polyphenyl-polyisocyanate is interposed both between the hub comprised of metallic parts and the boundary of the elastic body and between the massive body comprised of metallic parts and the boundary of the elastic body, and the non-slide effect can be obtained both at the place between the hub and the elastic body and between the massive body and the elastic body at the same time.
The damper of the present invention is obtained by the following procedures:
a. Applying a non-slide agent having polymethylene-polyphenyl-polyisocyanate onto at least one of a surface selected from a group of an outer peripheral surface of the outer peripheral side of the hub or an inner peripheral surface of the massive body or a surface of the elastic body,
b. Drying the hub or massive body or the elastic body so as to prevent from dripping of polymethylene-polyphenyl-polyisocyanate,
c. Press-fitting an elastic body between the hub and the massive body to form an assembly,
d. Cleaning the assembly in a solvent to remove dusts, and
e. Heating the assembly to react the none-slide agent.
Applying process and press-fitting process is essential for the present invention. But drying, cleaning and heating processes can be eliminated from the processes, for example, in order to cut the cost of the production.
Applying the polymethylene-polyphenyl-polyisocyanate onto the surface of the hub or the massive body can be achieved by spray coating, brush coating or immersion coating or the like. The polymethylene-polyphenyl-polyisocyanate can be applied onto the hub only or the massive body only or both of these metal parts, or onto the elastic body only or both of the elastic body and the metal parts. And then the elastic body is press-fitted into the space between the hub and the massive body to assemble a damper.
It is essential that the non-slide agent comprises polymethylene-polyphenyl-polyisocyanate. Other chemical agents or solvents may be added into polymethylene-polyphenyl-polyisocyanate so far as substantial non-slide effect of the present invention can be observed.
Referring to the heating process, it is not necessarily to take this procedure because the reaction of polymethylene-polyphenyl-polyisocyanate occurs slowly under even at room temperature. But it is desirable to warm the assembly to accelerate the reaction speed. The desirable temperature of the heating process is not lower than 70xc2x0 C. because the reaction speed is considerably slow under this temperature, and not higher than the temperature that the elastic material can be decomposed. If NBR (acrylonitrile butadiene rubber) is used for the elastic material, for example, the desirable heating temperature is around 120xc2x0 C. and caution must be paid to keep the temperature not more than 170xc2x0 C. to avoid the decomposition of the rubber.
Almost all rubber like materials may be used in the present invention. Blend rubber can also used. NBR, EPDM, VAMAC, EPDM/VMAC rubber can be used preferably. Vulcanized rubber is more preferably used in the present invention.